1. Field of the Invention
In general, the present invention relates to systems and methods that warn medical personnel if an improper radiation dosage has been selected for a particular patient. More particularly, the present invention relates to software applications that provide graphical indications of radiation dose ranges and warnings of potential dangers.
2. Prior Art Description
There are many medical conditions that can be treated with radiation therapy. However, one of the most important applications of radiation therapy is its use in treating cancer inside the body. If cancer cells can be located within the human body, then those cancer cells can be targeted with beams of radiation. The radiation carries enough energy to kill the cancer cells as the radiation impinges upon the cancer cells. In this manner, cancer cells can be killed deep within tissue masses.
The radiation beams begin at different physical points. Each individual radiation beam has a low dose that is insufficient to damage cells by itself. In this manner, the beams of radiation can reach the cancer cells without damaging healthy tissue along the path. The multiple beams of radiation all converge at the point of the cancer cells. The combined dose from the multiple beams of radiation then becomes sufficient to kill the cancer cells.
A problem associated with radiation therapy is that the level of radiation increases as the beams of radiation approach the treatment area. Consequently, the tissue surrounding the tumor is subjected to significant levels of radiation. Likewise, the tissue along each path of the radiation beams is also subjected to some radiation dose.
No two cancers are alike. Each cancer patient has cancer cells that are unique in location and mass to that patient. As such, the best way to direct beams of radiation onto cancer cells has become a complicated science. Physicians and dosimetrists must determine where to position the beams of radiation during radiation therapy in order to have the maximum effect on the cancer cells and the minimal effect on surrounding healthy tissue. Doctors and dosimetrists also try to avoid radiation dose to critical organ tissue, provided that tissue is healthy.
In the prior art, the manner in which a physician or dosimetrist plans a course of radiation therapy is a multi-step process. In the first step, the physician pinpoints the exact location of the cancer cells to be targeted. This is traditionally done using three-dimensional body imaging equipment, such as an MRI scan, a CAT scan, a PET scan or the like. Once the physician locates the target cancer cells, the physician/dosimetrist enters the outlines of the patient's anatomy into a computer that is running a treatment planning system. The treatment planning system runs software that computes a dose for all the anatomical structures that were entered into the system. The doses of all entered anatomical structures are then summarized graphically in the form of a dose volume histogram (DVH). The use of a treatment planning system to create a dose volume histogram is shown in U.S. Pat. No. 6,560,311 to Shepard, entitled Method For Preparing A Radiation Therapy Plan.
The physician/dosimetrist utilizes the dose volume histograms to evaluate the dose distribution of radiation in and around the targeted cancer cells. The physician/dosimetrist can alter the dose, position, and direction of the various radiation beams to develop a plan that will kill the targeted cancer cells, yet minimize dose to surrounding tissue, especially critical organ tissue. In the last step, the radiation equipment is programmed to the settings developed using the treatment plan. The equipment is then ready for use on the patient.
It will be understood that the dose volume histogram generated for a particular cancer in a particular patient is unique. In the prior art, systems that are used to produce does volume histograms do not have ability to also chart safety limit information onto the dose volume histograms being produced. As such, a physician/dosimetrist must cross-reference the graphical information presented on the dose volume histogram with the non-graphic empirical data of radiation exposure charts and dose tolerance limits in order to determine if any safety threshold is being approached. Furthermore, since the prior art systems that generate the dose volume histogram do not reference safety data, such systems lack the ability to warn about a potentially unsafe condition.
Many prior art systems use treatment planning constraints for an algorithm to optimize the dose. However, due to conflicting constraints of the tissue mass and surrounding normal tissue, the actual resulting dose is usually either above or below the constraint. When radiation plans do not meet the desired doses, good dosimetrists develop skill at pre-emptively setting the treatment planning constraints to fictitious values to repeatedly goad the algorithm into providing better results than it normally could. The constraints given to the planning system then, have little to do with the actual human radiation dose tolerance limits, and these prior art systems do not evaluate the safety of the actual planned doses as compared to published dose tolerance limits.
A need therefore exists for a system and method that can actively inform a physician and/or dosimetrist that the settings selected for the radiation therapy surpass safe levels for any region of healthy tissue along the various radiation beam paths. This need is met by the present invention as described and claimed below.